South Korea dismissed North Korea's call Thursday to lift bilateral sanctions, again urging Pyongyang to apologize for its 2010 attack on a naval ship.

A set of economic sanctions on the North, imposed after its torpedo attack that killed 46 sailors, was a proper security-related measure for the "normal development" of inter-Korean relations, a senior unification ministry official told reporters.

He was responding to some media reports here on the May 24th Measure, one of the largest obstacles to Seoul-Pyongyang ties.

The South's steadfast stance came on the fifth anniversary of the sinking of the 1,200-ton warship, the Cheonan, which was on a routine patrol mission near the disputed inter-Korean sea border in the Yellow Sea.

"There is no change in the government's position that North Korea should take a responsible step (with regard to the Cheonan incident) that South Korean people can accept," the official said.

If talks with North Korea are resumed, the South will raise the issue and try to secure its responsible measure, he added.

Pyongyang has flatly denied its involvement in the Cheonan case, claiming it was fabricated by the United States seeking to expand its influence in Northeast Asia. (Yonhap)